title: Structural characterization of gephyrin by AFM and SAXS reveals a mixture of compact and extended states.
abstract: Gephyrin is a trimeric protein involved in the final steps of molybdenum-cofactor (Moco) biosynthesis and in the clustering of inhibitory glycine and GABAA receptors at postsynaptic specializations. Each protomer consists of stably folded domains (referred to as the G and E domains) located at either terminus and connected by a proteolytically sensitive linker of ∼150 residues. Both terminal domains can oligomerize in their isolated forms; however, in the context of the full-length protein only the G-domain trimer is permanently present, whereas E-domain dimerization is prevented. Atomic force microscopy (AFM) and small-angle X-ray scattering (SAXS) reveal a high degree of flexibility in the structure of gephyrin. The results imply an equilibrium between compact and extended conformational states in solution, with a preference for compact states. CD spectroscopy suggests that a partial compaction is achieved by interactions of the linker with the G and E domains. Taken together, the data provide a rationale for the role of the linker in the overall structure and the conformational dynamics of gephyrin.
authors.affiliation: Structural Biology, Rudolf Virchow Center for Experimental Biomedicine, University of Würzburg, Josef-Schneider-Strasse 2, 97080 Würzburg, Germany.
authors.forename: Bodo
authors.initials: B
authors.lastname: Sander
authors.forename: Giancarlo
authors.initials: G
authors.lastname: Tria
authors.forename: Alexander V
authors.initials: AV
authors.lastname: Shkumatov
authors.forename: Eun-Young
authors.initials: EY
authors.lastname: Kim
authors.forename: J Günter
authors.initials: JG
authors.lastname: Grossmann
authors.forename: Ingrid
authors.initials: I
authors.lastname: Tessmer
authors.forename: Dmitri I
authors.initials: DI
authors.lastname: Svergun
authors.forename: Hermann
authors.initials: H
authors.lastname: Schindelin
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure*; D002942:Circular Dichroism; D003067:Coenzymes / Q000096:biosynthesis / Q000737:chemistry; D018360:Crystallography, X-Ray; D029968:Escherichia coli Proteins / Q000235:genetics; D014644:Genetic Variation; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000648:ultrastructure*; D008667:Metalloproteins / Q000096:biosynthesis / Q000737:chemistry; D018625:Microscopy, Atomic Force / Q000379:methods; D056004:Molecular Dynamics Simulation; D000090006:Molybdenum Cofactors; D009433:Neural Inhibition / Q000235:genetics; D011487:Protein Conformation; D017510:Protein Folding; D055503:Protein Multimerization; D059748:Proteolysis; D011621:Pteridines / Q000737:chemistry; D051381:Rats; D011963:Receptors, GABA-A / Q000737:chemistry / Q000235:genetics; D018009:Receptors, Glycine / Q000737:chemistry / Q000235:genetics; D053838:Scattering, Small Angle; D014961:X-Ray Diffraction / Q000379:methods*
chemical_list: D002352:Carrier Proteins; D003067:Coenzymes; D029968:Escherichia coli Proteins; D008565:Membrane Proteins; D008667:Metalloproteins; D000090006:Molybdenum Cofactors; D011621:Pteridines; D011963:Receptors, GABA-A; D018009:Receptors, Glycine; C404104:Mog protein, E coli; C073441:gephyrin; C022261:molybdopterin
keywords: GABAA receptor; Moco biosynthesis; atomic force microscopy; ensemble-optimization method; gephyrin; glycine receptor; intrinsic disorder; receptor clustering; single-molecule analysis; small-angle X-ray scattering